1. Field of the Invention
The present invention relates a method for measuring the length and a relative moving speed of an object moving with respect to a point of observation from time sequence image data produced by using line scan cameras and the like, and a pattern recognition method and apparatus based on the resulting image data.
2. Description of the Related Art
An example of the method of measuring a speed of a moving object using a plurality of sensors is based on the use of two phototubes. In this method, two phototubes are placed apart in parallel, and the speed of the moving object is obtained from the timings of the object crossing the two photo tubes in successive instances, and is widely used for speed measurements of cars and other moving objects.
On the other hand, the following references are examples of the method for determining the speed and length of a moving object from images. “Traffic flow measurements using the double slit method” (reference 1, Road Traffic and Automobiles, The Institute of Electrical Engineers of Japan, Vol. RTA94-5, 1994) and “Traffic flow measurements using the double slit camera” (reference 2, The Institute of Electronics Engineers of Japan, Vol. 26, No. 3, 1997). These methods are based on providing imaginary slits within the images recorded using a general purpose video-camera and obtaining spatial time images by linking the images between the slits. Two slits are placed in the images, so that the moving speed and the length of the object are measured by obtaining the time interval for the object to pass through the two slits.
However, in the above related art, there are problems outlined in the following.
When either the observation point or the vehicle moves along a determined track, and considering the topics for measuring relative speeds, the length of the object and recognizing the pattern of the moving object using the conventional phototubes, it is necessary to position the phototubes so that they surround the object. Also, because it is not possible to obtain images by this technique, it is not possible to know what type of object had passed between the sensors. Therefore, it is necessary to visually confirm the nature of the object.
In the meantime, according to conventional video images, because the two slit planes are not parallel, the depth of field must be fixed first, so that the distance of movement between the actual slits can be determined separately. Also, the general purpose video camera can only record at 30 frames/second, so that if the object is moving at high speeds, it is not possible to produce precision measurement of speed. Also, there is no known method of measuring the relative speed of an object using the images taken by placing a camera on another moving object.